Can you use distilled water in an aquarium?

Yes, we can use distilled water in an aquarium. But it is better to avoid distilled water, because distilled water will be having no minerals in it. If you are that particular about using distilled water, you may use it, but remember to add essential minerals in distilled water before you use it.

Some distilled water can be used in small amounts, such as replacing evaporated water. However, fish need the minerals found in tap water (but not distilled water) to survive. To lower ammonia, try changing 25-50% of the water (it can be the regular water you use).